diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6f7b4e9..1d41152 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,17 @@
 
 ### Fixed
 
+- **Cop options are declared, so RuboCop stops calling them unsupported.**
+  `config/default.yml` documented `Libraries` (`Glyphs/IconResolution`) and
+  `Mappings` (`Glyphs/LegacyIconHelper`) only in comments, and never mentioned
+  `LibraryComponents` (`Glyphs/LegacyIconHelper`, `Glyphs/PreferLibraryComponent`)
+  at all. RuboCop derives its supported-parameter list from the keys actually
+  present in that file, so it warned `does not support <param> parameter` on
+  every run — for four working options, one of which
+  `Glyphs/LegacyIconHelper` itself tells you to add. Each is now declared with an
+  empty default (a no-op merge), so the options are validated instead of
+  reported, with behaviour unchanged. Refs #7
+
 - **Declaration harvest unwraps trailing `.freeze`.** `ICONS = { "x" => :car }.freeze`
   (and `%i[a b].freeze`) used to yield a Prism `CallNode`, so hash/array values
   were never collected. Cross-file dynamics (`PhosphorIcon(@icon)` in a shared
diff --git a/README.md b/README.md
index 2c6f3f0..07dd2a1 100644
--- a/README.md
+++ b/README.md
@@ -210,6 +210,10 @@ Glyphs/LegacyIconHelper:
   # Mappings replaces the built-in defaults (_lucide/_phosphor/_hero/_heroicon/_tabler):
   # Mappings:
   #   _custom: CustomIcon
+  # LibraryComponents merges over the built-in library => component map, so
+  # `icon("x", library: "customlib")` corrects to `CustomIcon("x")`:
+  # LibraryComponents:
+  #   customlib: CustomIcon
 ```
 
 ### Glyphs/IconResolution
@@ -239,6 +243,15 @@ Glyphs/IconResolution:
 Icon(:house, library: :lucide) # => LucideIcon(:house)
 ```
 
+```yaml
+Glyphs/PreferLibraryComponent:
+  Include:
+    - app/**/*.rb
+  # LibraryComponents merges over the built-in library => component map:
+  # LibraryComponents:
+  #   customlib: CustomIcon
+```
+
 ## Migrating an app off icon helpers
 
 1. Add `gem "glyphs"`, `include Glyphs` where the helpers used to be included.
diff --git a/config/default.yml b/config/default.yml
index efbc98c..ef73c4c 100644
--- a/config/default.yml
+++ b/config/default.yml
@@ -3,10 +3,13 @@ Glyphs/LegacyIconHelper:
   Enabled: true
   VersionAdded: '0.1.0'
   SafeAutoCorrect: true
-  # Mappings replaces the built-in defaults when set:
-  # Mappings:
+  # Replaces the built-in helper => component defaults when set, e.g.
   #   _lucide: LucideIcon
   #   _heroicon: HeroIcon
+  Mappings: {}
+  # Merges over the built-in library => component map, e.g.
+  #   customlib: CustomIcon
+  LibraryComponents: {}
   DefaultLibraryComponent: HeroIcon
 
 Glyphs/IconResolution:
@@ -14,12 +17,15 @@ Glyphs/IconResolution:
   Enabled: true
   VersionAdded: '0.1.0'
   IconsPath: app/assets/svg/icons
-  # Libraries merges over the built-in defaults:
-  # Libraries:
+  # Merges over the built-in component => directory/variant defaults, e.g.
   #   PhosphorIcon: { Dir: phosphor, DefaultVariant: light }
+  Libraries: {}
 
 Glyphs/PreferLibraryComponent:
   Description: 'Prefer library-specific components over generic Icon(..., library: ...).'
   Enabled: true
   VersionAdded: '0.1.0'
   SafeAutoCorrect: true
+  # Merges over the built-in library => component map, e.g.
+  #   customlib: CustomIcon
+  LibraryComponents: {}
diff --git a/spec/rubocop/cop/glyphs/icon_resolution_spec.rb b/spec/rubocop/cop/glyphs/icon_resolution_spec.rb
index ffabb9d..5814a52 100644
--- a/spec/rubocop/cop/glyphs/icon_resolution_spec.rb
+++ b/spec/rubocop/cop/glyphs/icon_resolution_spec.rb
@@ -135,6 +135,21 @@
     end
   end
 
+  context "with the declared empty Libraries default" do
+    let(:cop_config) { { "IconsPath" => "spec/fixtures/svg/icons", "Libraries" => {} } }
+
+    it "still resolves through the built-in library defaults" do
+      expect_offense(<<~RUBY)
+        PhosphorIcon(:locks)
+                     ^^^^^^ Icon `locks` not found in phosphor/regular. Did you mean `:lock`?
+      RUBY
+
+      expect_correction(<<~RUBY)
+        PhosphorIcon(:lock)
+      RUBY
+    end
+  end
+
   context "with a Libraries override" do
     let(:cop_config) do
       {
diff --git a/spec/rubocop/cop/glyphs/legacy_icon_helper_spec.rb b/spec/rubocop/cop/glyphs/legacy_icon_helper_spec.rb
index 60cec28..c132666 100644
--- a/spec/rubocop/cop/glyphs/legacy_icon_helper_spec.rb
+++ b/spec/rubocop/cop/glyphs/legacy_icon_helper_spec.rb
@@ -110,6 +110,24 @@
     RUBY
   end
 
+  context "with the declared empty Mappings and LibraryComponents defaults" do
+    let(:cop_config) { { "Mappings" => {}, "LibraryComponents" => {} } }
+
+    it "still applies the built-in helper mappings and library components" do
+      expect_offense(<<~RUBY)
+        _lucide(:house)
+        ^^^^^^^ Use `LucideIcon(...)` instead of `_lucide(...)`.
+        icon("check", library: "heroicons")
+        ^^^^ Use `HeroIcon(...)` instead of `icon(...)`.
+      RUBY
+
+      expect_correction(<<~RUBY)
+        LucideIcon(:house)
+        HeroIcon("check")
+      RUBY
+    end
+  end
+
   context "with custom Mappings" do
     let(:cop_config) { { "Mappings" => { "_custom" => "CustomIcon" } } }
 
diff --git a/spec/rubocop/cop/glyphs/prefer_library_component_spec.rb b/spec/rubocop/cop/glyphs/prefer_library_component_spec.rb
index fc97349..d156815 100644
--- a/spec/rubocop/cop/glyphs/prefer_library_component_spec.rb
+++ b/spec/rubocop/cop/glyphs/prefer_library_component_spec.rb
@@ -41,4 +41,19 @@
       Some::Icon(:house, library: :lucide)
     RUBY
   end
+
+  context "with the declared empty LibraryComponents default" do
+    let(:cop_config) { { "LibraryComponents" => {} } }
+
+    it "still applies the built-in library components" do
+      expect_offense(<<~RUBY)
+        Icon(:house, library: :lucide)
+        ^^^^ Use `LucideIcon(...)` instead of `Icon(..., library: ...)`.
+      RUBY
+
+      expect_correction(<<~RUBY)
+        LucideIcon(:house)
+      RUBY
+    end
+  end
 end
diff --git a/spec/rubocop/plugin_spec.rb b/spec/rubocop/plugin_spec.rb
index 5c1bbad..e7f11ca 100644
--- a/spec/rubocop/plugin_spec.rb
+++ b/spec/rubocop/plugin_spec.rb
@@ -26,4 +26,34 @@
     )
     expect(config.values).to all(include("Enabled" => true))
   end
+
+  # RuboCop builds its supported-parameter list from the keys present in
+  # `config/default.yml` (see `ConfigValidator#each_invalid_parameter`), so an
+  # option a cop reads but the file only documents in a comment is reported as
+  # unsupported on every run.
+  it "declares every cop_config parameter its cops read" do
+    default_config = YAML.safe_load_file(plugin.rules(nil).value)
+
+    undeclared = glyphs_cops.filter_map do |cop|
+      missing = cop_config_keys_read_by(cop) - default_config.fetch(cop.cop_name).keys
+      "#{cop.cop_name} reads undeclared #{missing.join(', ')}" if missing.any?
+    end
+
+    expect(undeclared).to be_empty
+  end
+
+  def glyphs_cops
+    RuboCop::Cop::Registry.global.cops.select { |cop| cop.badge.department == :Glyphs }
+  end
+
+  # A cop reads its options both directly and through the shared
+  # `RuboCop::Cop::Glyphs::*` mixins, so both sources have to be scanned.
+  def cop_config_keys_read_by(cop_class)
+    mixins = cop_class.included_modules.select { |mod| mod.name.to_s.start_with?("RuboCop::Cop::Glyphs::") }
+
+    [cop_class, *mixins]
+      .filter_map { |mod| Object.const_source_location(mod.name)&.first }
+      .flat_map { |path| File.read(path).scan(/cop_config\["([^"]+)"\]/).flatten }
+      .uniq
+  end
 end